For example, when a heating operation is performed by using an air-conditioning apparatus in winter, an outdoor heat exchanger mounted on an outdoor unit serves as an evaporator, and thus frost is formed on the outdoor heat exchanger in some cases. Examples of conventional disclosed air-conditioning apparatuses include an air-conditioning apparatus that performs a hot gas defrosting operation in which hot gas refrigerant discharged from a compressor is supplied to the outdoor heat exchanger, and an air-conditioning apparatus that performs a reverse-defrosting operation in which frost on the outdoor heat exchanger is removed by using heat of an indoor heat exchanger mounted on an indoor unit (refer to Patent Literature 1 and Patent Literature 2, for example).
The hot gas defrosting operation is not a defrosting operation using the heat of the indoor heat exchanger. In other words, in the hot gas defrosting operation, the indoor unit is not used as a heat radiating source. With this configuration, some heat remains in the indoor heat exchanger when a heating operation starts, thereby reducing an increase in a time required for a start-up of the heating operation.
In the reverse-defrosting operation, the indoor unit is used as a heat radiating source, and thus defrosting performance is achieved to be higher than that of the hot gas defrosting operation. Consequently, defrosting of the outdoor heat exchanger can be completed in a short time.